Lubricating oil compositions containing non-sulfur-phosphorus containing zinc compounds and method for preventing or reducing low speed pre-ignition in direct injected spark-ignited engines

ABSTRACT

A lubricant composition for a direct injected, boosted, spark ignited internal combustion engine that contains at least one non-sulfur-phosphorus containing zinc compound is disclosed. This disclosure also relates to a method for preventing or reducing low speed pre-ignition in an engine lubricated with a formulated oil. The formulated oil has a composition comprising at least one oil soluble or oil dispersible non-sulfur-phosphorus containing zinc compound.

FIELD OF THE INVENTION

This disclosure relates to a lubricant composition for a direct injected, boosted, spark ignited internal combustion engine that contains at least one non-sulfur-phosphorus containing zinc compound. This disclosure also relates to a method for preventing or reducing low speed pre-ignition in an engine lubricated with a formulated oil. The formulated oil has a composition comprising at least one oil soluble or oil dispersible non-sulfur-phosphorus zinc compound.

BACKGROUND OF THE INVENTION

One of the leading theories surrounding the cause of low speed pre-ignition (LSPI) is at least in part, due to auto-ignition of engine oil droplets that enter the engine combustion chamber from the piston crevice under high pressure, during periods in which the engine is operating at low speeds, and compression stroke time is longest (Amann et al. SAE 2012-01-1140). Although some engine knocking and pre-ignition problems can be and are being resolved through the use of new engine technology, such as electronic controls and knock sensors, and through the optimization of engine operating conditions, there is a role for lubricating oil compositions which can decrease or prevent the problem. The present inventors have discovered a solution for addressing the problem of LSPI through the use of non-sulfur-phosphorus zinc containing additives.

SUMMARY OF THE INVENTION

In an aspect, the present disclosure provides a method for preventing or reducing low speed pre-ignition in a direct injected, boosted, spark ignited internal combustion engine, said method comprising the step of lubricating the crankcase of the engine with a lubricating oil composition comprising from about 200 to about 3000 ppm of zinc metal from at least one non-sulfur-phosphorus containing zinc compound, based on the total weight of the lubricating oil.

For example, the non-sulfur-phosphorus containing zinc compound is a zinc alkoxide or thiolate compound, zinc aryloxide or arylthiolate compound, colloidal dispersion of zinc oxide, stable colloidal zinc suspension, zinc amido compound, zinc acetylacetonate compound, zinc carboxylate, zinc alkylhydroxybenzoate, zinc arylsulfonate, zinc sulfurized phenate, zinc dithiocarbamato complex, zinc salen complex, bimetallic zinc complex, zinc phosphate ester, zinc phospinate, zinc phosphinite complex, zinc pyridyl complex, zinc polypyridyl complex, zinc quinolinolato complex, zinc succinimide.

In yet another aspect, the present disclosure provides a lubricating engine oil composition for a direct injected, boosted, spark ignited internal combustion engine comprising from about 200 to about 3000 ppm of zinc metal from at least one non-sulfur-phosphorus containing zinc compound, based on the total weight of the lubricating oil.

DETAILED DESCRIPTION OF THE INVENTION Definitions

The term “boosting” is used throughout the specification. Boosting refers to running an engine at higher intake pressures than in naturally aspirated engines. A boosted condition can be reached by use of a turbocharger (driven by exhaust) or a supercharger (driven by the engine). Using smaller engines that provide higher power densities has allowed engine manufacturers to provide excellent performance while reducing frictional and pumping losses. This is accomplished by increasing boost pressures with the use of turbochargers or mechanical superchargers, and by down-speeding the engine by using higher transmission gear ratios allowed by higher torque generation at lower engine speeds. However, higher torque at lower engine speeds has been found to cause random pre-ignition in engines at low speeds, a phenomenon known as Low Speed Pre-Ignition, or LSPI, resulting in extremely high cylinder peak pressures, which can lead to catastrophic engine failure. The possibility of LSPI prevents engine manufacturers from fully optimizing engine torque at lower engine speed in such smaller, high-output engines.

Throughout the specification and claims the expression oil soluble or dispersible is used. By oil soluble or dispersible is meant that an amount needed to provide the desired level of activity or performance can be incorporated by being dissolved, dispersed or suspended in an oil of lubricating viscosity. Usually, this means that at least about 0.001% by weight of the material can be incorporated in a lubricating oil composition. For a further discussion of the terms oil soluble and dispersible, particularly “stably dispersible”, see U.S. Pat. No. 4,320,019 which is expressly incorporated herein by reference for relevant teachings in this regard.

The term “sulfated ash” as used herein refers to the non-combustible residue resulting from detergents and metallic additives in lubricating oil. Sulfated ash may be determined using ASTM Test D874.

The term “Total Base Number” or “TBN” as used herein refers to the amount of base equivalent to milligrams of KOH in one gram of sample. Thus, higher TBN numbers reflect more alkaline products, and therefore a greater alkalinity. TBN was determined using ASTM D 2896 test. Unless otherwise specified, all percentages are in weight percent.

In general, the level of sulfur in the lubricating oil compositions of the present invention is less than or equal to about 0.7 wt. %, based on the total weight of the lubricating oil composition, e.g., a level of sulfur of about 0.01 wt. % to about 0.70 wt. %, 0.01 to 0.6 wt. %, 0.01 to 0.5 wt. %, 0.01 to 0.4 wt. %, 0.01 to 0.3 wt. %, 0.01 to 0.2 wt. %, 0.01 wt. % to 0.10 wt. %. In one embodiment, the level of sulfur in the lubricating oil compositions of the present invention is less than or equal to about 0.60 wt. %, less than or equal to about 0.50 wt. %, less than or equal to about 0.40 wt. %, less than or equal to about 0.30 wt. %, less than or equal to about 0.20 wt. %, less than or equal to about 0.10 wt. % based on the total weight of the lubricating oil composition.

In one embodiment, the levels of phosphorus in the lubricating oil compositions of the present invention is less than or equal to about 0.12 wt. %, based on the total weight of the lubricating oil composition, e.g., a level of phosphorus of about 0.01 wt. % to about 0.12 wt. %. In one embodiment, the levels of phosphorus in the lubricating oil compositions of the present invention is less than or equal to about 0.11 wt. %, based on the total weight of the lubricating oil composition, e.g., a level of phosphorus of about 0.01 wt. % to about 0.11 wt. %. In one embodiment, the levels of phosphorus in the lubricating oil compositions of the present invention is less than or equal to about 0.10 wt. %, based on the total weight of the lubricating oil composition, e.g., a level of phosphorus of about 0.01 wt. % to about 0.10 wt. %. In one embodiment, the levels of phosphorus in the lubricating oil compositions of the present invention is less than or equal to about 0.09 wt. %, based on the total weight of the lubricating oil composition, e.g., a level of phosphorus of about 0.01 wt. % to about 0.09 wt. %. In one embodiment, the levels of phosphorus in the lubricating oil compositions of the present invention is less than or equal to about 0.08 wt. %, based on the total weight of the lubricating oil composition, e.g., a level of phosphorus of about 0.01 wt. % to about 0.08 wt. %. In one embodiment, the levels of phosphorus in the lubricating oil compositions of the present invention is less than or equal to about 0.07 wt. %, based on the total weight of the lubricating oil composition, e.g., a level of phosphorus of about 0.01 wt. % to about 0.07 wt. %. In one embodiment, the levels of phosphorus in the lubricating oil compositions of the present invention is less than or equal to about 0.05 wt. %, based on the total weight of the lubricating oil composition, e.g., a level of phosphorus of about 0.01 wt. % to about 0.05 wt. %.

In one embodiment, the level of sulfated ash produced by the lubricating oil compositions of the present invention is less than or equal to about 1.60 wt. % as determined by ASTM D 874, e.g., a level of sulfated ash of from about 0.10 to about 1.60 wt. % as determined by ASTM D 874. In one embodiment, the level of sulfated ash produced by the lubricating oil compositions of the present invention is less than or equal to about 1.00 wt. % as determined by ASTM D 874, e.g., a level of sulfated ash of from about 0.10 to about 1.00 wt. % as determined by ASTM D 874. In one embodiment, the level of sulfated ash produced by the lubricating oil compositions of the present invention is less than or equal to about 0.80 wt. % as determined by ASTM D 874, e.g., a level of sulfated ash of from about 0.10 to about 0.80 wt. % as determined by ASTM D 874. In one embodiment, the level of sulfated ash produced by the lubricating oil compositions of the present invention is less than or equal to about 0.60 wt. % as determined by ASTM D 874, e.g., a level of sulfated ash of from about 0.10 to about 0.60 wt. % as determined by ASTM D 874.

Suitably, the present lubricating oil composition may have a total base number (TBN) of 4 to 15 mg KOH/g (e.g., 5 to 12 mg KOH/g, 6 to 12 mg KOH/g, or 8 to 12 mg KOH/g). Low Speed Pre-Ignition is most likely to occur in direct-injected, boosted (turbocharged or supercharged), spark-ignited (gasoline) internal combustion engines that, in operation, generate a break mean effective pressure level of greater than about 15 bar (peak torque), such as at least about 18 bar, particularly at least about 20 bar at engine speeds of from about 1500 to about 2500 rotations per minute (rpm), such as at engine speeds of from about 1500 to about 2000 rpm. As used herein, break mean effective pressure (BMEP) is defined as the work accomplished during one engine cycle, divided by the engine swept volume; the engine torque normalized by engine displacement. The word “brake” denotes the actual torque/power available at the engine flywheel, as measured on a dynamometer. Thus, BMEP is a measure of the useful power output of the engine.

In one embodiment of the invention, the engine is operated at speeds between 500 rpm and 3000 rpm, or 800 rpm to 2800 rpm, or even 1000 rpm to 2600 rpm. Additionally, the engine may be operated with a break mean effective pressure of 10 bars to 30 bars, or 12 bars to 24 bars.

LSPI events, while comparatively uncommon, may be catastrophic in nature. Hence drastic reduction or even elimination of LSPI events during normal or sustained operation of a direct fuel injection engine is desirable. In one embodiment, the method of the invention is such that there are less than 15 LSPI events per 100,000 combustion events or less than 10 LSPI events per 100,000 combustion events. In one embodiment, there may be less than 5 LSPI events per 100,000 combustion events, less than 4 LSPI events per 100,000 combustion events, less than 3 LSPI events per 100,000 combustion events, less than 2 LSPI events per 100,000 combustion events, less than 1 LSPI event per 100,000 combustion events, or there may be 0 LSPI events per 100,000 combustion events.

Therefore, in an aspect the present disclosure provides a method for preventing or reducing low speed pre-ignition in a direct injected, boosted, spark ignited internal combustion engine, said method comprising the step of lubricating the crankcase of the engine with a lubricating oil composition comprising at least one non-sulfur-phosphorus containing zinc compound. In one embodiment, the amount of zinc metal from the at least one non-sulfur-phosphorus containing zinc compound is from about 200 to about 3000 ppm, or from about 250 to about 3000 ppm, from about 300 to about 3000 ppm, from about 350 to about 3000 ppm, from about 400 ppm to about 3000 ppm, from about 500 to about 3000 ppm, from about 600 to about 3000 ppm, from about 700 to about 3000 ppm, from about 900 to about 3000, from about 950 to about 3000 ppm, from about 1000 to 3000 ppm, from about 1050 to about 3000 ppm, from about 1100 to about 3000 ppm, from about 1200 to about 3000 ppm, from about 1300 to about 3000 ppm, from about 1400 to about 3000 ppm, or from about 1400 to 3000 ppm.

In one embodiment, the total amount of zinc in the formulation including the metal from the at least one non-sulfur-phosphorus containing zinc compound is from about 700 to about 4000 ppm, or from about 800 to about 4000 ppm, from about 900 to about 4000, from about 950 to about 4000 ppm, from about 1000 to 4000 ppm, from about 1050 to about 4000 ppm, from about 1100 to about 4000 ppm, from about 1200 to about 4000 ppm, from about 1300 to about 4000 ppm, from about 1400 to about 4000 ppm, or from about 1400 to 4000 ppm.

In one embodiment, the method of the invention provides a reduction in the number of LSPI events of at least 10 percent, or at least 20 percent, or at least 30 percent, or at least 50 percent, or at least 60 percent, or at least 70 percent, or at least 80 percent, or at least 90 percent, or at least 95 percent, compared to an oil that does not contain the at least one non-sulfur-phosphorus containing zinc compound.

In another aspect, the present disclosure provides a method for reducing the severity of low speed pre-ignition events in a direct injected, boosted, spark ignited internal combustion engine, said method comprising the step of lubricating the crankcase of the engine with a lubricating oil composition comprising at least one least one non-sulfur-phosphorus containing zinc compound. LSPI events are determined by monitoring peak cylinder pressure (PP) and mass fraction burn (MFB) of the fuel charge in the cylinder. When either or both criteria are met, it can be said that an LSPI event has occurred. The threshold for peak cylinder pressure varies by test, but is typically 4-5 standard deviations above the average cylinder pressure. Likewise, the MFB threshold is typically 4-5 standard deviations earlier than the average MFB (represented in crank angle degrees). LSPI events can be reported as average events per test, events per 100,000 combustion cycles, events per cycle, and/or combustion cycles per event. In one embodiment, the number of LSPI events where both MFB02 and Peak Pressure (PP) Requirements that were greater than 90 bar of pressure is less than 5 events, less than 4 events, less than 3 events, less than 2 events, or less than 1 event. In one embodiment, the number of LSPI events that were greater than 90 bar was zero events, or in other words completely suppressed LSPI events greater than 90 bar. In one embodiment, the number of LSPI events where both MFB02 and Peak Pressure (PP) Requirements that were greater than 100 bar of pressure is less than 5 events, less than 4 events, less than 3 events, less than 2 events, or less than 1 event. In one embodiment, the number of LSPI events that were greater than 100 bar was zero events, or in other words completely suppressed LSPI events greater than 100 bar. In one embodiment, the number of LSPI events where both MFB02 and Peak Pressure (PP) Requirements that were greater than 110 bar of pressure is less than 5 events, less than 4 events, less than 3 events, less than 2 events, or less than 1 event. In one embodiment, the number of LSPI events that were greater than 110 bar was zero events, or in other words completely suppressed LSPI events greater than 110 bar. For example, the number of LSPI events where both MFB02 and Peak Pressure (PP) Requirements that were greater than 120 bar of pressure is less than 5 events, less than 4 events, less than 3 events, less than 2 events, or less than 1 event. In one embodiment, the number of LSPI events that were greater than 120 bar was zero events, or in other words completely suppressed very severe LSPI events (i.e., events greater than 120 bar).

It has now been found that the occurrence of LSPI in engines susceptible to the occurrence of LSPI can be reduced by lubricating such engines with lubricating oil compositions containing a non-sulfur-phosphorus containing zinc compound.

The disclosure further provides the method described herein in which the engine is fueled with a liquid hydrocarbon fuel, a liquid nonhydrocarbon fuel, or mixtures thereof.

The disclosure further provides the method described herein in which the engine is fueled by natural gas, liquefied petroleum gas (LPG), compressed natural gas (CNG), or mixtures thereof.

Lubricating oil compositions suitable for use as passenger car motor oils conventionally comprise a major amount of oil of lubricating viscosity and minor amounts of performance enhancing additives, including ash-containing compounds. Conveniently, zinc is introduced into the lubricating oil compositions used in the practice of the present disclosure by one or more non-sulfur-phosphorus containing zinc compound.

Oil of Lubricating viscosity/Base Oil Component

The oil of lubricating viscosity for use in the lubricating oil compositions of this disclosure, also referred to as a base oil, is typically present in a major amount, e.g., an amount of greater than 50 wt. %, preferably greater than about 70 wt. %, more preferably from about 80 to about 99.5 wt. % and most preferably from about 85 to about 98 wt. %, based on the total weight of the composition. The expression “base oil” as used herein shall be understood to mean a base stock or blend of base stocks which is a lubricant component that is produced by a single manufacturer to the same specifications (independent of feed source or manufacturer's location); that meets the same manufacturer's specification; and that is identified by a unique formula, product identification number, or both. The base oil for use herein can be any presently known or later-discovered oil of lubricating viscosity used in formulating lubricating oil compositions for any and all such applications, e.g., engine oils, marine cylinder oils, functional fluids such as hydraulic oils, gear oils, transmission fluids, etc. Additionally, the base oils for use herein can optionally contain viscosity index improvers, e.g., polymeric alkylmethacrylates; olefinic copolymers, e.g., an ethylene-propylene copolymer or a styrene-diene copolymer; and the like and mixtures thereof.

As one skilled in the art would readily appreciate, the viscosity of the base oil is dependent upon the application. Accordingly, the viscosity of a base oil for use herein will ordinarily range from about 2 to about 2000 centistokes (cSt) at 100° Centigrade (C.). Generally, individually the base oils used as engine oils will have a kinematic viscosity range at 100° C. of about 2 cSt to about 30 cSt, preferably about 3 cSt to about 16 cSt, and most preferably about 4 cSt to about 12 cSt and will be selected or blended depending on the desired end use and the additives in the finished oil to give the desired grade of engine oil, e.g., a lubricating oil composition having an SAE Viscosity Grade of 0W, 0W-8, 0W-12, 0W-16, 0W-20, 0W-26, 0W-30, 0W-40, 0W-50, 0W-60, 5W, 5W-20, 5W-30, 5W-40, 5W-50, 5W-60, 10W, 10W-20, 10W-30, 10W-40, 10W-50, 15W, 15W-20, 15W-30, 15W-40, 30, 40 and the like.

Group I base oils generally refer to a petroleum derived lubricating base oil having a saturates content of less than 90 wt. % (as determined by ASTM D 2007) and/or a total sulfur content of greater than 300 ppm (as determined by ASTM D 2622, ASTM D 4294, ASTM D 4297 or ASTM D 3120) and has a viscosity index (VI) of greater than or equal to 80 and less than 120 (as determined by ASTM D 2270).

Group II base oils generally refer to a petroleum derived lubricating base oil having a total sulfur content equal to or less than 300 parts per million (ppm) (as determined by ASTM D 2622, ASTM D 4294, ASTM D 4927 or ASTM D 3120), a saturates content equal to or greater than 90 weight percent (as determined by ASTM D 2007), and a viscosity index (VI) of between 80 and 120 (as determined by ASTM D 2270).

Group III base oils generally refer to a petroleum derived lubricating base oil having less than 300 ppm sulfur, a saturates content greater than 90 weight percent, and a VI of 120 or greater.

Group IV base oils are polyalphaolefins (PAOs).

Group V base oils include all other base oils not included in Group I, II, III, or IV.

The lubricating oil composition can contain minor amounts of other base oil components. For example, the lubricating oil composition can contain a minor amount of a base oil derived from natural lubricating oils, synthetic lubricating oils or mixtures thereof. Suitable base oil includes base stocks obtained by isomerization of synthetic wax and slack wax, as well as hydrocracked base stocks produced by hydrocracking (rather than solvent extracting) the aromatic and polar components of the crude.

Suitable natural oils include mineral lubricating oils such as, for example, liquid petroleum oils, solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinic-naphthenic types, oils derived from coal or shale, animal oils, vegetable oils (e.g., rapeseed oils, castor oils and lard oil), and the like.

Suitable synthetic lubricating oils include, but are not limited to, hydrocarbon oils and halo-substituted hydrocarbon oils such as polymerized and interpolymerized olefins, e.g., polybutylenes, polypropylenes, propylene-isobutylene copolymers, chlorinated polybutylenes, poly(1-hexenes), poly(1-octenes), poly(1-decenes), and the like and mixtures thereof; alkylbenzenes such as dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes, di(2-ethylhexyl)-benzenes, and the like; polyphenyls such as biphenyls, terphenyls, alkylated polyphenyls, and the like; alkylated diphenyl ethers and alkylated diphenyl sulfides and the derivative, analogs and homologs thereof and the like.

Other synthetic lubricating oils include, but are not limited to, oils made by polymerizing olefins of less than 5 carbon atoms such as ethylene, propylene, butylenes, isobutene, pentene, and mixtures thereof. Methods of preparing such polymer oils are well known to those skilled in the art.

Additional synthetic hydrocarbon oils include liquid polymers of alpha olefins having the proper viscosity. Especially useful synthetic hydrocarbon oils are the hydrogenated liquid oligomers of C₆ to C₁₂ alpha olefins such as, for example, 1-decene trimer.

Another class of synthetic lubricating oils include, but are not limited to, alkylene oxide polymers, i.e., homopolymers, interpolymers, and derivatives thereof where the terminal hydroxyl groups have been modified by, for example, esterification or etherification. These oils are exemplified by the oils prepared through polymerization of ethylene oxide or propylene oxide, the alkyl and phenyl ethers of these polyoxyalkylene polymers (e.g., methyl poly propylene glycol ether having an average molecular weight of 1,000, diphenyl ether of polyethylene glycol having a molecular weight of 500-1000, diethyl ether of polypropylene glycol having a molecular weight of 1,000-1,500, etc.) or mono- and polycarboxylic esters thereof such as, for example, the acetic esters, mixed C₃-C₈ fatty acid esters, or the C₁₃ oxo acid diester of tetraethylene glycol.

Yet another class of synthetic lubricating oils include, but are not limited to, the esters of dicarboxylic acids e.g., phthalic acid, succinic acid, alkyl succinic acids, alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acids, alkyl malonic acids, alkenyl malonic acids, etc., with a variety of alcohols, e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol, etc. Specific examples of these esters include dibutyl adipate, di(2-ethylhexyl)sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid and the like.

Esters useful as synthetic oils also include, but are not limited to, those made from carboxylic acids having from about 5 to about 12 carbon atoms with alcohols, e.g., methanol, ethanol, etc., polyols and polyol ethers such as neopentyl glycol, trimethylol propane, pentaerythritol, dipentaerythritol, tripentaerythritol, and the like.

Silicon-based oils such as, for example, polyalkyl-, polyaryl-, polyalkoxy- or polyaryloxy-siloxane oils and silicate oils, comprise another useful class of synthetic lubricating oils. Specific examples of these include, but are not limited to, tetraethyl silicate, tetra-isopropyl silicate, tetra-(2-ethylhexyl) silicate, tetra-(4-methyl-hexyl)silicate, tetra-(p-tert-butylphenyl)silicate, hexyl-(4-methyl-2-pentoxy)disiloxane, poly(methyl)siloxanes, poly(methylphenyl)siloxanes, and the like. Still yet other useful synthetic lubricating oils include, but are not limited to, liquid esters of phosphorous containing acids, e.g., tricresyl phosphate, trioctyl phosphate, diethyl ester of decane phosphionic acid, etc., polymeric tetrahydrofurans and the like.

The lubricating oil may be derived from unrefined, refined and rerefined oils, either natural, synthetic or mixtures of two or more of any of these of the type disclosed hereinabove. Unrefined oils are those obtained directly from a natural or synthetic source (e.g., coal, shale, or tar sands bitumen) without further purification or treatment. Examples of unrefined oils include, but are not limited to, a shale oil obtained directly from retorting operations, a petroleum oil obtained directly from distillation or an ester oil obtained directly from an esterification process, each of which is then used without further treatment. Refined oils are similar to the unrefined oils except they have been further treated in one or more purification steps to improve one or more properties. These purification techniques are known to those of skill in the art and include, for example, solvent extractions, secondary distillation, acid or base extraction, filtration, percolation, hydrotreating, dewaxing, etc. Rerefined oils are obtained by treating used oils in processes similar to those used to obtain refined oils. Such rerefined oils are also known as reclaimed or reprocessed oils and often are additionally processed by techniques directed to removal of spent additives and oil breakdown products. Lubricating oil base stocks derived from the hydroisomerization of wax may also be used, either alone or in combination with the aforesaid natural and/or synthetic base stocks. Such wax isomerate oil is produced by the hydroisomerization of natural or synthetic waxes or mixtures thereof over a hydroisomerization catalyst.

Natural waxes are typically the slack waxes recovered by the solvent dewaxing of mineral oils; synthetic waxes are typically the wax produced by the Fischer-Tropsch process.

Other useful fluids of lubricating viscosity include non-conventional or unconventional base stocks that have been processed, preferably catalytically, or synthesized to provide high performance lubrication characteristics.

Non Sulfur-Phosphorus Containing Zinc Compound

The lubrication oil compositions herein can contain one or more non-sulfur phosphorus containing zinc compounds. Non-sulfur phosphorus containing zinc compounds is taken to mean that the zinc additive does not contain both phosphorus and sulfur in the bonding ligands, but may separately contain phosphorus or sulfur or neither of those atoms. Those skilled in the art will recognize suitable additives have been described in Stahl, L; et al., “Zinc Organometallics” in Comprehensive Organometallic Chemistry III; 1st Edition; Mingos, D. M. P.; Crabtree, R. H.; Meyer, K.; Eds.; Elsevier: Oxford, 2007, pp 311-412, and is incorporated herein by reference. The zinc complexes described in this disclosure are typically prepared by reacting a di- or tetravalent zinc reactant with a suitable ligand using methods apparent to a practitioner of ordinary skill in the art. The zinc complexes described are represented by their most simple molecular formulas, but it is understood in the art that aggregate, multinuclear, and cluster complexes may also exist in chemical equilibrium with the simplified molecular formula. The zinc complexes are generally accepted as meaning the product between a zinc reactant and a suitable ligand or ligands. Commonly used zinc reactants include, but are not limited to zinc oxide, zinc sulfide, zinc sulfate, zinc chloride, zinc chloride tetrahydrofuran complex, dichloro(N,N,N′,N′-tetramethylehtylenediamine) zinc, zinc bromide, zinc iodide, zinc fluoride, zinc methoxide, zinc phosphate, zinc stearate, zinc acetylacetonate, zinc acetate, zinc carbonate hydroxide, zinc naphthenate, or similar zinc compounds. Some zinc reagents may exist as a hydrated species. Any one of these zinc compounds described above can be used as the zinc compound of the present disclosure. Preferred zinc compounds are zinc oxide or zinc chloride. The zinc reactants can also be the zinc compound of the present disclosure as long as they do not contain both sulfur and phosphorus. The zinc complexes described herein are oil-soluble or oil dispersible.

In one embodiment, the zinc compound can be a zinc alkoxide or thiolate compound. For example, the zinc alkoxides or thiolates can be of the form Zn(YR_(A))_(n)L_(X) where Y is an oxygen or sulfur atom, R_(A) is a linear, cyclic, or branched, saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 20 carbon atoms, n is an integer from 0 to 2, L is a ligand that saturates the coordination sphere of zinc, and x is an integer from 0 to 4. In certain embodiments, the ligand, L, is selected from the group consisting of water, hydroxide, phosphine, phosphite, ammonia, amino, amido, alkylthiolate, halide, and combinations thereof so long as the zinc species does not contain both sulfur and phosphorus groups. For example, the zinc alkoxide can be zinc methoxide or the like.

In one embodiment, the zinc compound can be a zinc aryloxide or arylthiolate compound. For example, the zinc aryloxide or arylthiolate is of the following Formula 1:

where R_(B) is a hydrogen atom or a linear, cyclic, or branched, saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 30 carbon atoms, Y is an oxygen atom or sulfur atom, n is an integer from 0 to 2, L is a ligand that saturates the coordination sphere of zinc, and x is an integer from 0 to 4. In certain embodiments, the ligand, L, is selected from the group consisting of water, hydroxide, phosphine, phosphite, ammonia, amino, amido, alkylthiolate, halide, and combinations thereof so long as the zinc species does not contain both sulfur and phosphorus groups.

In one embodiment, the zinc compound can be a colloidal dispersion of zinc oxide. For example, zinc oxide has the net molecular formula of ZnO, but can comprise repeating [Zn—O—Zn]_(n) units. In certain embodiments, the colloidal dispersion of zinc oxide will comprise an average nanoparticle size <100 nm as determined by microscopic techniques such as TEM. To assist in the dispersion of the colloidal particles a solvent can be added. For example, US 20160237373, incorporated herein by reference, teaches that a C₁-C₃ alcohol solvent can be used to disperse zinc oxide nanoparticles in oil. Generally, the amount of the colloidal dispersion of zinc oxide can be from about 0.01 wt. % to about 5 wt. %.

In another embodiment, the zinc compound can be a stable colloidal suspension. For example, U.S. Pat. No. 7,884,058, incorporated herein by reference, discloses stable colloidal suspensions of various inorganic oxides. These can be prepared in the presence of an oil phase with a dispersing agent that includes polyalkylene succinic anhydrides, non-nitrogen containing derivatives of a polyalkylene succinic anhydride selected from the group consisting of a polyalkylene succinic acid, a Group I and/or Group II mono- or di-salt of a polyalkylene succinic acid, a polyalkylene succinate ester formed by the reaction of a polyalkylene succinic anhydride or an acid chloride with an alcohol and mixtures thereof, and mixtures thereof and a diluent oil, wherein the stable colloidal suspension is substantially clear.

In one embodiment, the zinc compound can be a zinc amido compound. For example, the zinc amido compound can be of the form Zn(NR_(C))_(n)L_(X) where R_(C) is a trimethylsilyl group or a linear, cyclic, or branched, and saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 20 carbon atoms, n is an integer from 0 to 2, L is a ligand that saturates the coordination sphere of zinc, and x is an integer from 0 to 4. In certain embodiments, the ligand, L, is selected from the group consisting of water, hydroxide, phosphine, phosphite, ammonia, amino, amido, alkylthiolate, halide, and combinations thereof so long as the zinc species does not contain both sulfur and phosphorus groups.

In one embodiment, the zinc compound can be a zinc acetylacetonate compound. For example, the zinc acetylacetonate is of the following Formula 2:

where R_(D) can be a symmetric or asymmetric linear, cyclic, or branched, saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 20 carbon atoms, or an aromatic moiety, n is an integer from 0 to 2, L is a ligand that saturates the coordination sphere of zinc, and x is an integer from 0 to 4. In certain embodiments, the ligand, L, is selected from the group consisting of water, hydroxide, phosphine, phosphite, ammonia, amino, amido, alkylthiolate, halide, and combinations thereof so long as the zinc species does not contain both sulfur and phosphorus groups.

In one embodiment, the zinc compound can be a zinc carboxylate. For example, the zinc carboxylate is of the following Formula 3:

where R_(E) can be a linear, cyclic, or branched, saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 50 carbon atoms, or aromatic and alkylaromatic rings with alkyl groups that can be linear, cyclic, or branched, and saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 20 carbon atoms, n is an integer from 0 to 2, L is a ligand that saturates the coordination sphere of zinc, and x is an integer from 0 to 4. In certain embodiments, the zinc carboxylate can form small clusters of the form Zn₃(O₂CR_(E))₆L_(x). In certain embodiments, O₂CR_(E) can represent a napthenate residue, which is generally understood to be complex mixtures of cycloaliphatic residues obtained by oxidation of naphtha. In certain embodiments, the ligand, L, is selected from the group consisting of water, hydroxide, phosphine, phosphite, ammonia, amino, amido, alkylthiolate, halide, and combinations thereof so long as the zinc species does not contain both sulfur and phosphorus groups. For example, the zinc carboxylate can be zinc stearate or another fatty acid. The zinc carboxylate can also be, for example, zinc octoate or zinc 2-ethylhexanoate.

In one embodiment, the zinc compound can be a zinc alkylhydroxybenzoate. For example, the zinc salicylate is of the following Formula 4:

where R_(F) is a hydrogen atom, a linear, cyclic, or branched, saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 30 carbon atoms, p is an integer from 1 to 2, n is an integer from 0 to 2, L is a ligand that saturates the coordination sphere of zinc, and x is an integer from 0 to 4. Particularly, n is an integer from 0 to 2. In certain embodiments, the ligand, L, is selected from the group consisting of water, hydroxide, phosphine, phosphite, ammonia, amino, amido, alkylthiolate, halide, and combinations thereof so long as the zinc species does not contain both sulfur and phosphorus groups. In one embodiment, the alkylhydroxybenzoate is a salicylate. In some embodiments, alkali earth metals such as magnesium, calcium, strontium, and barium may be added. Alkali earth metals are typically basic salts which can include, but are not limited to, metal oxides, metal alkoxides, metal carbonates, and metal bicarbonates.

In another embodiment, the zinc compound can be a zinc arylsulfonate. For example, the zinc arylsufonate is of the following Formula 5:

where R_(G) is a hydrogen atom, a linear, cyclic, or branched, saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 30 carbon atoms, p is an integer from 1 to 5, n is an integer from 0 to 2, L is a ligand that saturates the coordination sphere of zinc, and x is an integer from 0 to 4. Particularly, n is an integer from 0 to 2. Particularly, p is 1 or 2. In certain embodiments, the ligand, L, is selected from the group consisting of water, hydroxide, phosphine, phosphite, ammonia, amino, amido, alkylthiolate, halide, and combinations thereof so long as the zinc species does not contain both sulfur and phosphorus groups. In some embodiments, alkali earth metals such as magnesium, calcium, strontium, and barium may be added. Alkali earth metals are typically basic salts which can include, but are not limited to, metal oxides, metal alkoxides, metal carbonates, and metal bicarbonates.

In one embodiment, the zinc compound can be a zinc sulfurized phenate. For example, the zinc sulfurized phenate is of the following Formula 6:

where R_(H) is a hydrogen atom, a linear, cyclic, or branched, saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 30 carbon atoms, x′ is an integer from 1 to zinc 8, n is an integer from 1 to about 15, L is a ligand that saturates the coordination sphere of zinc, and x is an integer from 0 to 4. Particularly, n is an integer from 1 to about 5. In certain embodiments, the ligand, L, is selected from the group consisting of water, hydroxide, phosphine, phosphite, ammonia, amino, amido, alkylthiolate, halide, and combinations thereof so long as the zinc species does not contain both sulfur and phosphorus groups. In some embodiments, alkali earth metals such as magnesium, calcium, strontium, and barium may be added. Alkali earth metals are typically basic salts which can include, but are not limited to, metal oxides, metal alkoxides, metal carbonates, and metal bicarbonates.

In one embodiment, the zinc compound can be a zinc dithiocarbamato complex. For example, the zinc dithiocarbamate is of Formula 7:

where each R_(I) is independently a linear, cyclic, or branched, saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 10 carbon atoms, n is an integer from 0 to 2, L is a ligand that saturates the coordination sphere of zinc, and x is an integer from 0 to 4. In certain embodiments, the ligand, L, is selected from the group consisting of water, hydroxide, ammonia, amino, amido, alkylthiolate, halide, and combinations thereof.

In one embodiment, the zinc compound can be a salen complex. For example, the zinc salen is of Formula 8:

where each R_(J) is independently a hydrogen atom, or a linear, cyclic, or branched, saturated or unsaturated, hydrocarbon moiety having from 1 to about 8 carbon atoms, each Y is independently —C(R_(J″))_(z) where R_(J″) is a hydrogen atom, a linear, cyclic, or branched, saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 8 carbon atoms, or an aromatic ring, z is 1 or 2 when N is imido or amino, respectively, each R_(J′) is independently a hydrogen atom, or a linear, cyclic, or branched, saturated or unsaturated, aliphatic chains hydrocarbon moiety having from 1 to about 8 carbon atoms, or taken together with the atoms to which they are connected form a 5-, 6-, or 7-membered ring (can be aromatic, completely saturated, or contain varying levels of unsaturation), n is an integer from 0 to 2, L is a ligand that saturates the coordination sphere of zinc, and x is an integer from 0 to 4. In certain embodiments, the ligand, L, is selected from the group consisting of water, hydroxide, phosphine, phosphite, ammonia, amino, amido, alkylthiolate, halide, and combinations thereof so long as the zinc species does not contain both sulfur and phosphorus groups.

In one embodiment, the zinc compound can be a bimetallic zinc complex. For example, the bimetallic zinc complex is of Formula 9:

where R_(K) is a hydrogen atom, or a linear, cyclic, or branched, saturated or unsaturated, hydrocarbon moiety having from 1 to about 30 carbon atoms, each R_(K″) is independently a hydrogen atom, a linear, cyclic, or branched, saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 8 carbon atoms, or an aromatic ring, each R_(K′) is independently a hydrogen atom, or a linear, cyclic, or branched, saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 8 carbon atoms, or taken together with the atoms to which they are connected form a 5-, 6-, or 7-membered ring (can be completely saturated or contain varying levels of unsaturation), L is a ligand that saturates the coordination sphere of the zincs, and x is an integer from 0 to 4. In certain embodiments, the ligand, L, is selected from the group consisting of water, hydroxide, phosphine, phosphite, ammonia, amino, amido, alkylthiolate, halide, and combinations thereof so long as the zinc species does not contain both sulfur and phosphorus groups.

In one embodiment, the zinc compound can be a phosphate ester, phospinate, or phosphinite complex. For example, the zinc phosphate esters, phosphite, phospinates, or phosphinites are of the following Formula 10:

where W is an oxo or an unbonded pair of electrons when the phosphorous atom is in the +5 or +3 oxidation state, respectively, each R_(L) is independently a linear, cyclic, or branched, saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 10 carbon atoms, an aromatic ring or an alkoxide moiety, n is an integer from 0 to 2, L is a ligand that saturates the coordination sphere of zinc, and x is an integer from 0 to 4. In some embodiments, the zinc phosphate esters, phosphite, phospinates, and phosphinites structures are dimeric with bridging ligand groups. In certain embodiments, the ligand, L, is selected from the group consisting of water, hydroxide, phosphine, phosphite, ammonia, amino, amido, halide, and combinations thereof.

In one embodiment, the zinc compound can be pyridyl, polypyridyl, and quinolinolato complexes. For example, pyridyl, polypyridyl, and quinolinolato complexes of zinc are of the following Formula 11:

where R_(M) is independently a hydrogen atom or a linear, cyclic, or branched, saturated or unsaturated, aliphatic hydrocarbon moiety having from 1 to about 10 carbon atoms, a pyridyl ring typically substituted at the 2 position which can be unfuctionalized or can be connected to the other functionalized pyridyl rings to make fused ring systems commonly referred to 8-hydroxyquinolines, quinolines, or phenanthrolines, n is an integer from 0 to 2, L is a ligand that saturates the coordination sphere of zinc, and x is an integer from 0 to 4. In certain embodiments, the ligand, L, is selected from the group consisting of water, hydroxide, phosphine, phosphite, ammonia, amino, amido, alkylthiolate, halide, and combinations thereof so long as the zinc species does not contain both sulfur and phosphorus groups.

In one embodiment, a zinc reactant can be complexed to a basic nitrogen dispersant succinimide. The basic nitrogen succinimide used to prepare the zinc complexes has at least one basic nitrogen and is preferably oil-soluble. The succinimide compositions may be post-treated with, e.g., boron, using procedures well known in the art so long as the compositions continue to contain basic nitrogen. The mono and polysuccinimides that can be used to prepare the zinc complexes described herein are disclosed in numerous references and are well known in the art. Certain fundamental types of succinimides and the related materials encompassed by the term of art “succinimide” are taught in U.S. Pat. Nos. 3,219,666; 3,172,892; and 3,272,746, the disclosures of which are hereby incorporated by reference. The term “succinimide” is understood in the art to include many of the amide, imide, and amidine species which may also be formed. The predominant product however is a succinimide and this term has been generally accepted as meaning the product of a reaction of an alkenyl substituted succinic acid or anhydride with a nitrogen-containing compound. Preferred succinimides, because of their commercial availability, are those succinimides prepared from a hydrocarbyl succinic anhydride, wherein the hydrocarbyl group contains from about 24 to about 350 carbon atoms, and an ethylene amine, said ethylene amines being especially characterized by ethylene diamine, diethylene triamine, triethylene tetramine, and tetraethylene pentamine. Particularly preferred are those succinimides prepared from polyisobutenyl succinic anhydride of 70 to 128 carbon atoms and tetraethylene pentamine or triethylene tetramine or mixtures thereof. Also included within the term “succinimide” are the cooligomers of a hydrocarbyl succinic acid or anhydride and a poly secondary amine containing at least one tertiary amino nitrogen in addition to two or more secondary amino groups. Ordinarily this composition has between 1,500 and 50,000 average molecular weight. A typical compound would be that prepared by reacting polyisobutenyl succinic anhydride and ethylene dipiperazine.

Succinimides having an average molecular weight of 1000 or 1300 or 2300 and mixtures thereof are most preferred.

Generally, the amount of the non-sulfur-phosphorus containing zinc compound can be from about 0.001 wt. % to about 25 wt. %, from about 0.05 wt. % to about 20 wt. %, or from about 0.1 wt. % to about 15 wt. %, or from about 0.5 wt. % to about 5 wt. %, from about, 1.0 wt. % to about 4.0 wt. %, based on the total weight of the lubricating oil composition.

In an aspect, the present disclosure provides a lubricating engine oil composition for a direct injected, boosted, spark ignited internal combustion engine comprising at least one non-sulfur-phosphorus containing zinc compound. In one embodiment, the amount of metal from the at least one non-sulfur-phosphorus containing zinc compound is from about 200 to about 3000 ppm, or from about 250 to about 3000 ppm, from about 300 to about 3000 ppm, from about 350 to about 3000 ppm, from about 400 ppm to about 3000 ppm, from about 500 to about 3000 ppm, from about 600 to about 3000 ppm, from about 700 to about 3000 ppm, from about 900 to about 3000, from about 950 to about 3000 ppm, from about 1000 to 3000 ppm, from about 1050 to about 3000 ppm, from about 1100 to about 3000 ppm, from about 1200 to about 3000 ppm, from about 1300 to about 3000 ppm, from about 1400 to about 3000 ppm, or from about 1400 to 3000 ppm.

In an aspect, the present disclosure provides a lubricating engine oil composition for a direct injected, boosted, spark ignited internal combustion engine comprising at least one non-sulfur-phosphorus containing zinc compound and a ZnDTP. In one embodiment, the amount of metal from the at least one non-sulfur-phosphorus containing zinc compound and ZnDTP is from about 700 to about 4000 ppm, or from about 800 to about 4000 ppm, from about 900 to about 4000, from about 950 to about 4000 ppm, from about 1000 to 4000 ppm, from about 1050 to about 4000 ppm, from about 1100 to about 4000 ppm, from about 1200 to about 4000 ppm, from about 1300 to about 4000 ppm, from about 1400 to about 4000 ppm, or from about 1400 to 4000 ppm.

In an aspect, the present disclosure provides a method for improving deposit control performance while at the same time preventing or reducing low speed pre-ignition in a direct injected, boosted, spark ignited internal combustion engine, said method comprising the step of lubricating the crankcase of the engine with a lubricating oil composition comprising at least one non-sulfur-phosphorus containing zinc compound. In one embodiment, the zinc compounds does not contain sulfur or phosphorus. In one embodiment, the zinc compound is a zinc carboxylate as described herein.

Generally, the amount of the non-sulfur-phosphorus containing zinc compound can be from about 0.001 wt. % to about 25 wt. %, from about 0.05 wt. % to about 20 wt. %, or from about 0.1 wt. % to about 15 wt. %, or from about 0.1 wt. % to about 5 wt. %, from about, 0.1 wt. % to about 4.0 wt. %, based on the total weight of the lubricating oil composition.

In one embodiment, the non-sulfur-phosphorus containing zinc compound can be combined with conventional lubricating oil detergent additives which contain magnesium and/or calcium. In one embodiment the calcium detergent(s) can be added in an amount sufficient to provide the lubricating oil composition from 0 to about 2400 ppm of calcium metal, from 0 to about 2200 ppm of calcium metal, from 100 to about 2000 ppm of calcium metal, from 200 to about 1800 ppm of calcium metal, or from about 100 to about 1800 ppm, or from about 200 to about 1500 ppm, or from about 300 to about 1400 ppm, or from about 400 to about 1400 ppm, of calcium metal in the lubricating oil composition. In one embodiment the magnesium detergent(s) can be added in an amount sufficient to provide the lubricating oil composition from about 100 to about 1000 ppm of magnesium metal, or from about 100 to about 600 ppm, or from about 100 to about 500 ppm, or from about 200 to about 500 ppm of magnesium metal in the lubricating oil composition.

In one embodiment, the non-sulfur-phosphorus containing zinc compound can be combined with conventional lubricating oil detergent additives which contain lithium. In one embodiment the lithium detergent(s) can be added in an amount sufficient to provide the lubricating oil composition from 0 to about 2400 ppm of lithium metal, from 0 to about 2200 ppm of lithium metal, from 100 to about 2000 ppm of lithium metal, from 200 to about 1800 ppm of lithium metal, or from about 100 to about 1800 ppm, or from about 200 to about 1500 ppm, or from about 300 to about 1400 ppm, or from about 400 to about 1400 ppm, of lithium metal in the lubricating oil composition.

In one embodiment, the non-sulfur-phosphorus containing zinc compound can be combined with conventional lubricating oil detergent additives which contain sodium. In one embodiment the sodium detergent(s) can be added in an amount sufficient to provide the lubricating oil composition from 0 to about 2400 ppm of sodium metal, from 0 to about 2200 ppm of sodium metal, from 100 to about 2000 ppm of sodium metal, from 200 to about 1800 ppm of sodium metal, or from about 100 to about 1800 ppm, or from about 200 to about 1500 ppm, or from about 300 to about 1400 ppm, or from about 400 to about 1400 ppm, of sodium metal in the lubricating oil composition.

In one embodiment, the non-sulfur-phosphorus containing zinc compound can be combined with conventional lubricating oil detergent additives which contain potassium. In one embodiment the potassium detergent(s) can be added in an amount sufficient to provide the lubricating oil composition from 0 to about 2400 ppm of potassium metal, from 0 to about 2200 ppm of potassium metal, from 100 to about 2000 ppm of potassium metal, from 200 to about 1800 ppm of potassium metal, or from about 100 to about 1800 ppm, or from about 200 to about 1500 ppm, or from about 300 to about 1400 ppm, or from about 400 to about 1400 ppm, of potassium metal in the lubricating oil composition.

In one embodiment, the disclosure provides a lubricating engine oil composition comprising a lubricating oil base stock as a major component; and at least one non-sulfur-phosphorus containing zinc compound, as a minor component; and wherein the engine exhibits greater than 50% reduced low speed pre-ignition, based on normalized low speed pre-ignition (LSPI) counts per 100,000 engine cycles, engine operation at between 500 and 3,000 revolutions per minute and brake mean effective pressure (BMEP) between 10 and 30 bar, as compared to low speed pre-ignition performance achieved in an engine using a lubricating oil that does not comprise the at least one non-sulfur-phosphorus containing zinc compound.

In one aspect, the disclosure provides a lubricating engine oil composition for use in a down-sized boosted engine comprising a lubricating oil base stock as a major component; and at least one non-sulfur-phosphorus containing zinc compound, as a minor component; where the downsized engine ranges from about 0.5 to about 3.6 liters, from about 0.5 to about 3.0 liters, from about 0.8 to about 3.0 liters, from about 0.5 to about 2.0 liters, or from about 1.0 to about 2.0 liters. The engine can have two, three, four, five or six cylinders.

In an aspect, the present disclosure provides the use of a at least one non-sulfur-phosphorus containing zinc compound for preventing or reducing low speed pre-ignition in a direct injected, boosted, spark ignited internal combustion engine.

Lubricating Oil Additives

In addition to the zinc compound described herein, the lubricating oil composition can comprise additional lubricating oil additives.

The lubricating oil compositions of the present disclosure may also contain other conventional additives that can impart or improve any desirable property of the lubricating oil composition in which these additives are dispersed or dissolved. Any additive known to a person of ordinary skill in the art may be used in the lubricating oil compositions disclosed herein. Some suitable additives have been described in Mortier et al., “Chemistry and Technology of Lubricants”, 2nd Edition, London, Springer, (1996); and Leslie R. Rudnick, “Lubricant Additives: Chemistry and Applications”, New York, Marcel Dekker (2003), both of which are incorporated herein by reference. For example, the lubricating oil compositions can be blended with antioxidants, anti-wear agents, metal detergents, rust inhibitors, dehazing agents, demulsifying agents, metal deactivating agents, friction modifiers, pour point depressants, antifoaming agents, co-solvents, corrosion-inhibitors, ashless dispersants, multifunctional agents, dyes, extreme pressure agents and the like and mixtures thereof. A variety of the additives are known and commercially available. These additives, or their analogous compounds, can be employed for the preparation of the lubricating oil compositions of the disclosure by the usual blending procedures.

The lubricating oil composition of the present invention can contain one or more detergents. Metal-containing or ash-forming detergents function as both detergents to reduce or remove deposits and as acid neutralizers or rust inhibitors, thereby reducing wear and corrosion and extending engine life. Detergents generally comprise a polar head with a long hydrophobic tail.

The polar head comprises a metal salt of an acidic organic compound. The salts may contain a substantially stoichiometric amount of the metal in which case they are usually described as normal or neutral salts. A large amount of a metal base may be incorporated by reacting excess metal compound (e.g., an oxide or hydroxide) with an acidic gas (e.g., carbon dioxide).

Detergents that may be used include oil-soluble neutral and overbased sulfonates, phenates, sulfurized phenates, thiophosphonates, salicylates, and naphthenates and other oil-soluble carboxylates of a metal, particularly the alkali or alkaline earth metals, e.g., barium, sodium, potassium, lithium, calcium, and magnesium. The most commonly used metals are calcium and magnesium, which may both be present in detergents used in a lubricant, and mixtures of calcium and/or magnesium with sodium.

The lubricating oil composition of the present invention can contain one or more anti-wear agents that can reduce friction and excessive wear. Any anti-wear agent known by a person of ordinary skill in the art may be used in the lubricating oil composition. Non-limiting examples of suitable anti-wear agents include zinc dithiophosphate, metal (e.g., Pb, Sb, Mo and the like) salts of dithiophosphates, metal (e.g., Zn, Pb, Sb, Mo and the like) salts of dithiocarbamates, metal (e.g., Zn, Pb, Sb and the like) salts of fatty acids, boron compounds, phosphate esters, phosphite esters, amine salts of phosphoric acid esters or thiophosphoric acid esters, reaction products of dicyclopentadiene and thiophosphoric acids and combinations thereof The amount of the anti-wear agent may vary from about 0.01 wt. % to about 5 wt. %, from about 0.05 wt. % to about 3 wt. %, or from about 0.1 wt. % to about 1 wt. %, based on the total weight of the lubricating oil composition.

In certain embodiments, the anti-wear agent is or comprises a dihydrocarbyl dithiophosphate metal salt, such as zinc dialkyl dithiophosphate compounds. The metal of the dihydrocarbyl dithiophosphate metal salt may be an alkali or alkaline earth metal, or aluminum, lead, tin, molybdenum, manganese, nickel or copper. In some embodiments, the metal is zinc. In other embodiments, the alkyl group of the dihydrocarbyl dithiophosphate metal salt has from about 3 to about 22 carbon atoms, from about 3 to about 18 carbon atoms, from about 3 to about 12 carbon atoms, or from about 3 to about 8 carbon atoms. In further embodiments, the alkyl group is linear or branched.

The amount of the dihydrocarbyl dithiophosphate metal salt including the zinc dialkyl dithiophosphate salts in the lubricating oil composition disclosed herein is measured by its phosphorus content. In some embodiments, the phosphorus content of the lubricating oil composition disclosed herein is from about 0.01 wt. % to about 0.14 wt. %, based on the total weight of the lubricating oil composition.

The lubricating oil composition of the present invention can contain one or more friction modifiers that can lower the friction between moving parts. Any friction modifier known by a person of ordinary skill in the art may be used in the lubricating oil composition. Non-limiting examples of suitable friction modifiers include fatty carboxylic acids; derivatives (e.g., alcohol, esters, borated esters, amides, metal salts and the like) of fatty carboxylic acid; mono-, di- or tri-alkyl substituted phosphoric acids or phosphonic acids; derivatives (e.g., esters, amides, metal salts and the like) of mono-, di- or tri-alkyl substituted phosphoric acids or phosphonic acids; mono-, di- or tri-alkyl substituted amines; mono- or di-alkyl substituted amides and combinations thereof. In some embodiments examples of friction modifiers include, but are not limited to, alkoxylated fatty amines; borated fatty epoxides; fatty phosphites, fatty epoxides, fatty amines, borated alkoxylated fatty amines, metal salts of fatty acids, fatty acid amides, glycerol esters, borated glycerol esters; and fatty imidazolines as disclosed in U.S. Pat. No. 6,372,696, the contents of which are incorporated by reference herein; friction modifiers obtained from a reaction product of a C₄ to C₇₅, or a C₆ to C₂₄, or a C₆ to C₂₀, fatty acid ester and a nitrogen-containing compound selected from the group consisting of ammonia, and an alkanolamine and the like and mixtures thereof. The amount of the friction modifier may vary from about 0.01 wt. % to about 10 wt. %, from about 0.05 wt. % to about 5 wt. %, or from about 0.1 wt. % to about 3 wt. %, based on the total weight of the lubricating oil composition.

The lubricating oil composition of the disclosure can contain a molybdenum-containing friction modifier. The molybdenum-containing friction modifier can be any one of the known molybdenum-containing friction modifiers or the known molybdenum-containing friction modifier compositions.

Preferred molybdenum-containing friction modifier is, for example, sulfurized oxymolybdenum dithiocarbamate, sulfurized oxymolybdenum dithiophosphate, amine-molybdenum complex compound, oxymolybdenum diethylate amide, and oxymolybdenum monoglyceride. Most preferred is a molybdenum dithiocarbamate friction modifier.

The lubricating oil composition of the invention generally contains the molybdenum-containing friction modifier in an amount of 0.01 to 0.15 wt. % in terms of the molybdenum content.

The lubricating oil composition of the invention preferably contains an organic oxidation inhibitor in an amount of 0.01-5 wt. %, preferably 0.1-3 wt. %. The oxidation inhibitor can be a hindered phenol oxidation inhibitor or a diarylamine oxidation inhibitor. The diarylamine oxidation inhibitor is advantageous in giving a base number originating from the nitrogen atoms. The hindered phenol oxidation inhibitor is advantageous in producing no NOx gas. Examples of the hindered phenol oxidation inhibitors include 2,6-di-t-butyl-p-cresol, 4,4′-methylenebis(2,6-di-t-butylphenol), 4,4′-methylenebis(6-t-butyl-o-cresol), 4,4′-isopropylidenebis(2,6-di-t-butylphenol), 4,4′-bis(2,6-di-t-butylphenol), 2,2′-methylenebis(4-methyl-6-t-butylphenol), 4,4′-thiobis(2-methyl-6-t-butylphenol), 2,2-thio-diethylenebis [3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, octadecyl3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and octyl 3-(3,54-butyl-4-hydroxy-3-methylphenyl)propionate, and commercial products such as, but not limited to, Irganox L135® (BASF), Naugalube 531® (Chemtura), and Ethanox 376® (SI Group).

Examples of the diarylamine oxidation inhibitors include alkyldiphenylamine having a mixture of alkyl groups of 4 to 9 carbon atoms, p,p′-dioctyldiphenylamine, phenyl-naphthylamine, phenyl-naphthylamine, alkylated-naphthylamine, and alkylated phenyl-naphthylamine. Each of the hindered phenol oxidation inhibitor and diarylamine oxidation inhibitor can be employed alone or in combination. If desired, other oil soluble oxidation inhibitors can be employed in combination with the above-mentioned oxidation inhibitor(s).

The lubricating oil composition of the invention may further contain an oxymolybdenum complex of succinimide, particularly a sulfur-containing oxymolybdenum complex of succinimide. The sulfur-containing oxymolybdenum complex of succinimide can provide increased oxidation inhibition when it is employed in combination with the above-mentioned phenolic or amine oxidation inhibitors.

In the preparation of lubricating oil formulations, it is common practice to introduce the additives in the form of 10 to 80 wt. % active ingredient concentrates in hydrocarbon oil, e.g. mineral lubricating oil, or other suitable solvent.

Usually these concentrates may be diluted with 3 to 100, e.g., 5 to 40, parts by weight of lubricating oil per part by weight of the additive package in forming finished lubricants, e.g. crankcase motor oils. The purpose of concentrates, of course, is to make the handling of the various materials less difficult and awkward as well as to facilitate solution or dispersion in the final blend.

Processes of Preparing Lubricating Oil Compositions

The lubricating oil compositions disclosed herein can be prepared by any method known to a person of ordinary skill in the art for making lubricating oils. In some embodiments, the base oil can be blended or mixed with the non-sulfur-phosphorus containing zinc compound described herein. Optionally, one or more other additives in additional to the non-sulfur-phosphorus containing zinc compound can be added. The non-sulfur-phosphorus containing zinc compound and the optional additives may be added to the base oil individually or simultaneously. In some embodiments, the non-sulfur-phosphorus containing zinc compound and the optional additives are added to the base oil individually in one or more additions and the additions may be in any order. In other embodiments, the non-sulfur-phosphorus containing zinc compound and the additives are added to the base oil simultaneously, optionally in the form of an additive concentrate. In some embodiments, the solubilizing of the non-sulfur-phosphorus containing zinc compound or any solid additives in the base oil may be assisted by heating the mixture to a temperature from about 25° C. to about 200° C., from about 50° C. to about 150° C. or from about 75° C. to about 125° C.

Any mixing or dispersing equipment known to a person of ordinary skill in the art may be used for blending, mixing or solubilizing the ingredients. The blending, mixing or solubilizing may be carried out with a blender, an agitator, a disperser, a mixer (e.g., planetary mixers and double planetary mixers), a homogenizer (e.g., Gaulin homogenizers and Rannie homogenizers), a mill (e.g., colloid mill, ball mill and sand mill) or any other mixing or dispersing equipment known in the art.

Application of the Lubricating Oil Compositions

The lubricating oil composition disclosed herein may be suitable for use as motor oils (that is, engine oils or crankcase oils), in a spark-ignited internal combustion engine, particularly a direct injected, boosted, engine that is susceptible to low speed pre-ignition.

The following examples are presented to exemplify embodiments of the invention but are not intended to limit the invention to the specific embodiments set forth. Unless indicated to the contrary, all parts and percentages are by weight. All numerical values are approximate. When numerical ranges are given, it should be understood that embodiments outside the stated ranges may still fall within the scope of the invention. Specific details described in each example should not be construed as necessary features of the invention.

EXAMPLES

The following examples are intended for illustrative purposes only and do not limit in any way the scope of the present invention.

Baseline Formulation

The base line formulation contained a Group 3 base oil, mixture of primary and secondary dialkyl zinc dithiophosphates in an amount to provide 770 ppm phosphorus and 890 ppm Zn to the lubricating oil composition, mixture of polyisobutenyl succinimide dispersants (borated and ethylene carbonate post-treated), a molybdenum succinimide complex in an amount to provide 180 ppm molybdenum to the lubricating oil composition, alkylated diphenylamine antioxidant, a borated friction modifier, foam inhibitor, a pour point depressant, and an olefin copolymer viscosity index improver.

The lubricating oil compositions were blended into a 5W-30 viscosity grade oil.

Zinc Compound A

The zinc compound A was prepared a from a C₁₄-C₁₈ alkylphenol with CO₂ and ZnO to form a low overbased Zn Salicylate (3.8% Zn) with a TBN of 66 based on the additive concentrate (35% diluent oil).

Zinc Compound B

The zinc compound B is a Zinc dithiocarbamate (i.e., (bis((dibutylcarbamothioyl)thio) zinc)) (13.79% Zn).

Zinc Compound C

The zinc compound C is a Zinc 2-ethylhexanoate (17.86% Zn).

Example 1

A lubricating oil composition was prepared by adding 1809 ppm of the zinc compound A and 2177 ppm of calcium from a combination of overbased Ca sulfonate and phenate detergents to the baseline formulation.

Example 2

A lubricating oil composition was prepared by adding 1798 ppm of the zinc compound B and 2320 ppm of calcium from a combination of overbased Ca sulfonate and phenate detergents to the baseline formulation.

Example 3

A lubricating oil composition was prepared by adding 1616 ppm of the zinc compound C and 2177 ppm of calcium from a combination of overbased Ca sulfonate and phenate detergents to the baseline formulation.

Example 4

A lubricating oil composition was prepared by adding 774 ppm of the zinc compound C and 1860 ppm of calcium from a combination of overbased Ca sulfonate and phenate detergents to the baseline formulation.

Example 5

A lubricating oil composition was prepared by adding 1626 ppm of the zinc compound C and 1935 ppm of calcium from a combination of overbased Ca sulfonate and phenate detergents to the baseline formulation.

Example 6

A lubricating oil composition was prepared by adding 2488 ppm of the zinc compound C and 2150 ppm of calcium from a combination of overbased Ca sulfonate and phenate detergents to the baseline formulation.

Comparative Example 1

A lubricating oil composition was prepared by adding 2148 ppm of calcium from a combination of overbased Ca sulfonate phenate detergents to the baseline formulation.

Comparative Example 2

A lubricating oil composition was prepared by adding 1858 ppm of calcium from a combination of overbased Ca sulfonate phenate detergents to the baseline formulation.

LSPI Testing

Low Speed Pre-ignition events were measured in a Ford 2.0L Ecoboost engine. This engine is a turbocharged gasoline direct injection (GDI) engines.

The Ford LSPI test is operated in four-4 hours iterations. The engine is operated at 1750 rpm and 1.7 MPa break mean effective pressure (BMEP) with an oil sump temperature of 95° C. The engine is run for 175,000 combustion cycles in each stage.

LSPI events are determined by monitoring peak cylinder pressure (PP) and mass fraction burn (MFB) of the fuel charge in the cylinder. When either or both criteria are met, it can be said that an LSPI event has occurred. The threshold for peak cylinder pressure varies by test, but is typically 4-5 standard deviations above the average cylinder pressure. Likewise, the MFB threshold is typically 4-5 standard deviations earlier than the average MFB (represented in crank angle degrees). LSPI events can be reported as average events per test, events per 100,000 combustion cycles, events per cycle, and/or combustion cycles per event. The results for this test is shown below.

TABLE 1 Ford LSPI Test Results Ex. 1 Ex. 2 Ex. 3 Ex. 6 Comp. Ex. 1 Zn (ppm) 2699 (1809 from 2688 (1798 from 2506 (1616 from Zn 3378 (2488 from Zn 932 from Zn Salicylate, Zn DTC, 2-ethylhexanoate, 890 2-ethylhexanoate, ZnDTP 890 from ZnDTP) 890 from ZnDTP) from ZnDTP) 890 from ZnDTP) Ca (ppm) 2177 2320 2177 2150 2148 Average Cycles* 3.5 5 4.75 9 19.25 Average Cycles* > 90 bar 1.75 2.5 2.5 5.5 12 11 Average Cycles* > 100 bar 1.5 2.5 2.25 5.25 11 Average Cycles* > 110 bar 1.25 2.25 2 4.5 9.5 Average Cycles* > 120 bar 1 1.5 2 3.5 8.5 Ex. 4 Ex. 5 Comp. Ex. 2 Zn (ppm) 1664 (774 from Zn 2516 (1626 from Zn 888 from 2-ethylhexanoate, 2-ethylhexanoate, ZnDTP 890 from ZnDTP) 890 from ZnDTP) Ca (ppm) 1860 1937 1858 Average Cycles* 6.75 5.5 9.25 Average Cycles* > 90 bar 5.25 2 4.5 Average Cycles* > 100 bar 4.25 1.75 4.25 Average Cycles* > 110 bar 4.25 1.5 3.75 Average Cycles* > 120 bar 3.25 1 3.5 *Counts all cycles of LSPI where both MFB02 and Peak Pressure Requirements are met Additionally, a GM 2.0 L LHU 4-cylinder gasoline turbocharged direct-injected engine was used for LSPI testing. Each cylinder was equipped with a combustion pressure sensor.

The data shows that Applicant's inventive example comprising a non-sulfur-phosphorus zinc compound provided significantly better LSPI performance both in terms of number of events but also the severity of LSPI events than the baseline example which did not contain the non-sulfur-phosphorus containing zinc compound in the Ford engines. 

What is claimed is:
 1. A method for preventing or reducing low speed pre-ignition in a direct injected, boosted, spark ignited internal combustion engine, said method comprising the step of lubricating the crankcase of the engine with a lubricating oil composition comprising from about 200 to about 3000 ppm of zinc metal from at least one non-sulfur-phosphorus containing zinc compound, based on the total weight of the lubricating oil composition.
 2. The method of claim 1, wherein the engine is operated under a load with a break mean effective pressure (BMEP) of from about 12 to about 30 bars.
 3. The method of claim 1, wherein the engine is operated at speeds between 500 and 3,000 rpm.
 4. The method of claim 1, wherein the non-sulfur-phosphorus containing zinc compound is a zinc alkoxide or thiolate compound, zinc aryloxide or arylthiolate compound, colloidal dispersion of zinc oxide, stable colloidal zinc suspension, zinc amido compound, zinc acetylacetonate compound, zinc carboxylate, zinc alkylhydroxybenzoate, zinc arylsulfonate, zinc sulfurized phenate, zinc dithiocarbamato complex, zinc salen complex, bimetallic zinc complex, zinc phosphate ester, zinc phospinate, zinc phosphinite complex, zinc pyridyl complex, zinc polypyridyl complex, zinc quinolinolato complex, zinc succinimide.
 5. The method of claim 1, wherein the lubricating oil composition further comprises a detergent selected from calcium detergent, magnesium detergent, sodium detergent, lithium detergent, and potassium detergent.
 6. The method of claim 5, wherein the detergent is a carboxylate, salicylate, phenate, or sulfonate detergent.
 7. The method of claim 1, wherein the lubricating oil further comprises a molybdenum containing compound.
 8. The method of claim 1, wherein the lubricating oil composition further comprises at least one other additive selected from an ashless dispersant, an ashless antioxidant, a phosphorus-containing anti-wear additive, a friction modifier, and a polymeric viscosity modifier.
 9. A lubricating engine oil composition for a direct injected, boosted, spark ignited internal combustion engine comprising from about 200 to about 3000 ppm of zinc metal from at least one non-sulfur-phosphorus containing zinc compound, based on the total weight of the lubricating oil.
 10. The lubricating engine oil composition of claim 9, wherein the non-sulfur-phosphorus containing zinc compound is a zinc alkoxide or thiolate compound, zinc aryloxide or arylthiolate compound, colloidal dispersion of zinc oxide, stable colloidal zinc suspension, zinc amido compound, zinc acetylacetonate compound, zinc carboxylate, zinc alkylhydroxybenzoate, zinc arylsulfonate, zinc sulfurized phenate, zinc dithiocarbamato complex, zinc salen complex, bimetallic zinc complex, zinc phosphate ester, zinc phospinate, zinc phosphinite complex, zinc pyridyl complex, zinc polypyridyl complex, zinc quinolinolato complexe, zinc succinimide.
 11. The lubricating engine oil composition of claim 9, wherein the lubricating oil composition further comprises a detergent selected from calcium detergents, magnesium detergents, sodium detergents, lithium detergents, and potassium detergents.
 12. The lubricating engine oil composition of claim 11, wherein the detergent is a carboxylate, salicylate, phenate, or sulfonate detergent.
 13. The lubricating engine oil composition of claim 9, wherein the lubricating oil composition further comprises a molybdenum containing compound.
 14. The lubricating engine oil composition of claim 9, wherein the lubricating oil composition further comprises at least one other additive selected from an ashless dispersant, an ashless antioxidant, a phosphorus-containing anti-wear additive, a friction modifier, and a polymeric viscosity modifier.
 15. Use of at least one non-sulfur-phosphorus containing zinc compound in a lubricating engine oil composition for preventing or reducing low speed pre-ignition in a direct injected, boosted, spark ignited internal combustion engine.
 16. Use of claim 15, wherein the at least one non-sulfur-phosphorus containing zinc compound is present in from about 200 to about 3000 ppm of metal from the at least one non-sulfur-phosphorus containing zinc compound, based on the total weight of the lubricating oil composition.
 17. A method for improving deposit control performance while at the same time preventing or reducing low speed pre-ignition in a direct injected, boosted, spark ignited internal combustion engine, said method comprising the step of lubricating the crankcase of the engine with a lubricating oil composition comprising at least one non-sulfur-phosphorus containing zinc compound.
 18. The method of claim 17, wherein the zinc compound does not contain sulfur or phosphorus.
 19. The method of claim 18, wherein zinc compound is a zinc carboxylate.
 20. Use of a lubricating engine oil composition in a down-sized boosted engine, wherein the lubricating engine oil composition comprises a lubricating oil base stock as a major component; and at least one non-sulfur-phosphorus containing zinc compound, as a minor component; wherein the downsized engine ranges from 0.5 liters to 3.6 liters. 